setting up irony-mode json compilation database

Question

I am struggling with the setup for irony-mode's JSON cdb support. I have this in my initialization:

;;; C++ code completion 
(eval-after-load 'company
  '(add-to-list 'company-backends 'company-irony))
(add-hook 'irony-mode-hook 'company-irony-setup-begin-commands)
(eval-after-load 'flycheck
  '(add-hook 'flycheck-mode-hook #'flycheck-irony-setup))
(add-hook 'c++-mode-hook 'flycheck-mode)
(add-hook 'c-mode-hook 'flycheck-mode)
(add-hook 'c++-mode-hook 'irony-mode)
(add-hook 'c-mode-hook 'irony-mode)
(add-hook 'objc-mode-hook 'irony-mode)

;; replace the `completion-at-point' and `complete-symbol' bindings in
;; irony-mode's buffers by irony-mode's function
(defun my-irony-mode-hook ()
  (define-key irony-mode-map [remap completion-at-point]
    'irony-completion-at-point-async)
  (define-key irony-mode-map [remap complete-symbol]
    'irony-completion-at-point-async))
(add-hook 'irony-mode-hook 'my-irony-mode-hook)
(add-hook 'irony-mode-hook 'irony-cdb-autosetup-compile-options)

(eval-after-load 'company
  '(add-to-list 'company-backends 'company-irony))

;; (optional) adds CC special commands to `company-begin-commands' in order to
;; trigger completion at interesting places, such as after scope operator
;;     std::|
(add-hook 'irony-mode-hook 'company-irony-setup-begin-commands)

I've tried running irony-cdb-json-add-compile-commands-path and setting the project root and compile_commands.json (generated using CMake), but when i go back to irony-cdb-menu, it just tells me that there is no compilation database in use. Any thoughts? Thanks! :)

Answer 1

How silly of me!

Turns out I had been setting the project root to the source directory rather than the build directory. If set to build directory irony-cdb works great!

In addition, to set additional compile options, it's useful to set irony-additional-clang-options, and naturally, putting these into a script.